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What is Mast Cell Activation Syndrome? How do I know if I have it?

Updated On:
April 2024
David Harris

About Mast Cell Activation Syndrome

Overview of Mast Cell Activation Syndrome

Mast Cell Activation Syndrome (MCAS) is a type of Mast Cell Disease. It is a disorder in which the mast cells in the body become overly active and release too many mediator chemicals, such as histamine, which can lead to a wide range of symptoms. These symptoms can include skin rashes, itching, flushing, abdominal pain, diarrhea, nausea, vomiting, headaches, and difficulty breathing. Symptoms may occur in response to a variety of triggers, such as stress, temperature changes, certain foods, medications, and other environmental factors.

MCAS can be challenging to diagnose, as it can mimic other conditions and symptoms can be variable and unpredictable. However, there are certain tests and evaluations that can help determine if someone has MCAS, such as a blood test to check for elevated levels of certain chemicals, or a skin biopsy to look for signs of mast cell activation.

Treatment for MCAS typically involves a combination of medications, such as antihistamines, mast cell stabilizers, and leukotriene inhibitors, as well as lifestyle modifications to help reduce triggers and manage symptoms. With proper management, many people with MCAS are able to lead healthy, fulfilling lives. It's important to work closely with a healthcare provider experienced in the diagnosis and treatment of MCAS to develop a personalized plan of care.

Prevalence of MCAS

MCAS is a complex and relatively uncommon condition, and its exact prevalence is not yet known. However, estimates suggest that it may affect between 10% to 17% of the general population. The prevalence of MCAS may be higher in individuals with certain comorbidities, such as Ehlers-Danlos Syndrome and dysautonomia. More research is needed to better understand the prevalence of MCAS and its associated comorbidities.

Diagnosis of Mast Cell Activation Syndrome

Identifying Symptoms of Mast Cell Activation Syndrome:

Mast Cell Activation Syndrome (MCAS) can be a challenging condition to diagnose, and it often takes several diagnostic stages to confirm a full diagnosis. The diagnosis process can take many years, as it is complex and requires testing for mast cell mediators, which can be difficult to identify. The first stage of MCAS diagnosis involves assessing whether two or more body systems are affected during a reaction, which is characteristic of multi-systemic conditions like MCAS. Symptoms of MCAS can vary greatly between individuals and may wax and wane over time, making it difficult to identify a specific pattern.

Response to Treatment for Mast Cell Activation Syndrome:

An important early step is determining whether MCAS symptoms improve with certain medications. This may involve a medication trial, where the person takes a known MCAS medication and their symptoms are monitored for improvement. If symptoms improve, a diagnosis of MCAS is more likely.

Testing for MCAS:

It is helpful to perform tests to identify higher than normal levels of chemical mediators in the body, which can be tested for in the blood or urine. Testing for IgE-mediated allergies is often one of the first tests performed by doctors, typically through skin prick tests or blood tests. However, these tests are usually inconclusive or negative in cases of idiopathic MCAS. A blood test to evaluate tryptase levels is often performed, but it is considered less specific for MCAS as many people with MCAS do not have high baseline tryptase levels. Other mast cell mediators can be tested for with a 24-hour urine collection, such as methylhistamine and prostaglandins.

It is often best to take these tests during a symptom flare, when symptoms may be particularly severe. In addition, some tests may need to be performed in the absence of particular medications, which should be discussed with a healthcare professional. Biopsies may also be taken from the gut, bladder, or skin to evaluate the presence of high or abnormal mast cell numbers, which can support a diagnosis of MCAS or mastocytosis.

Unfortunately, there are currently no genetic tests available for diagnosing MCAS, although research is underway to develop them.

Ruling out other conditions:

It is important to also rule out other possible causes of symptoms, as many conditions can overlap with MCAS. These include other types of Mast Cell Disease. During the diagnostic process, it is important to ensure that other potential diagnoses are not missed, and additional investigations such as endoscopy, colonoscopy, imaging, and biopsies may be required. It is important to rule out other conditions such as heart attacks, hepatitis, cancer, epilepsy, eosinophilic esophagitis, Addison's disease, and diabetes.

Seek an Expert Medical Opinion:

It's important to work closely with a healthcare provider experienced in the diagnosis and treatment of MCAS to complete these diagnostic stages and develop a personalized plan of care. We can help you find a doctor who is able to diagnose and treat MCAS.  While the diagnostic process can be challenging and frustrating, a confirmed diagnosis of MCAS is essential for appropriate management and treatment of symptoms.  

Comorbidites of Mast Cell Activation Syndrome

Mast Cell Activation Syndrome (MCAS) is often associated with other medical conditions, with individuals typically having at least one additional condition. The relationship between MCAS and many of these comorbidities is not yet fully understood, and more research is required.

Common comorbidities with MCAS include connective tissue disorders like Ehlers Danlos Syndrome (EDS), and dysautonomia like Postural Orthostatic Tachycardia Syndrome (POTS). Type 2 diabetes is also another common comorbidity. In addition to these more common comorbidities, there are many other associated conditions including hypermobility spectrum disorders (HSD), chronic fatigue syndrome (CFS) or myalgic encephalomyelitis (ME), fibromyalgia, irritable bowel syndrome (IBS), migraine, asthma, allergies (including food allergies), Marfans, chronic obstructive pulmonary disease (COPD), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and multiple sclerosis (MS).

It is important for individuals with MCAS to receive comprehensive medical care to address any comorbidities that may be present. A healthcare provider experienced in the management of MCAS and its associated conditions can help develop a personalized plan of care.

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